ABALONE: A NEW TOOL FOR UNDERSTANDING UPWELLING IN THE CALIFORNIA CURRENT (Invited Presentation)

Upwelling is a critical oceanographic driver of nutrient cycling in coastal environments. Nutrient-rich conditions associated with upwelling encourage primary productivity, forming the foundation of coastal ecosystems and fisheries. However, the often limited spatial and temporal resolution of paleoenvironmental reconstructions of upwelling and productivity constrains our understanding of how past basin-wide variability over long periods of time have impacted local ecosystems throughout the past. Nevertheless, understanding ecosystem responses to environmental variability requires data with sub-seasonal to seasonal resolution. Such high-resolution data may provide additional insight into seasonal extremes that impact the survival of coastal organisms (e.g., surface temperature, salinity, precipitation, etc.). Traditional environmental archives (e.g., sediment and ice cores) most often provide decadal resolution at best; however, biomineralizers such as mollusks can provide invaluable high-resolution time series from stable isotopic and growth analyses of their calcium carbonate shells. This presentation discusses preliminary data exploring the potential of analyzing a suite of stable nitrogen (δ¹⁵N), oxygen (δ¹⁸O), and carbon (δ¹³C) isotope data from analysis of Pacific abalone shells (Haliotis cracherodii). We present sub-seasonal δ¹⁵N time series data that, together with δ¹⁸O and δ¹³C, reflect seasonal variability closely linked to upwelling. Implications of this research are twofold: 1) Isotopic analyses from abalone shells may provide detailed knowledge on primary productivity during upwelling and as well as limited productivity when upwelling is greatly reduced and 2) archaeological shell middens in the Channel Islands contain an abundance of both abalone dating back to the early Holocene, presenting the opportunity to reconstruct upwelling throughout the Holocene.